Thermal operated circuit controlling device



June 11,1940.

o. s. FIELD THERMAL OPERATED CIRCUIT CONTROLLING DEVICE 2 Shets-Sheet 1 Original Filed Aug. 15, 1934 FIGUL June 11, 1940. o. s. FIELD 2,204,481

THERMAL OPERATED CIRCUIT CONTROLLING DEVICE Original Filed Aug. 15, 1934 2 Sheets-Sheet 2 Um BY Mum ATTORNEY Patented June 11, 1940 PATENT OFFICE THERMAL OPERATED CIRCUIT CONTROLLING DEVICE Oscar S. Field, Rochester, N. Y., assignor to General Railway Signal Company,

Rochester,

Original application August 15, 1934, Serial No.

739,981, new Patent No. 2,109,169, dated February 22-, 1938.

ZDivided and this application August 13, 1937, Serial No. 159,396

2 Claims.

This invention relates to circuit controlling devices of the thermal element type.

The present application is a division of my pending application Ser. No. 739,981, filed August 15, 1934, for Thermal operated circuit controlling devices, now Patent 2,109,169, granted February 22, 1938.

The heating and cooling of lei-metallic thermal elements in response to the flow and interruption of electric current may be advantageously employed to open or close contacts on a time interval basis. In the interests 01" economy and eiliciency, such thermal elements may be enclosed in an evacuated or gas filled bulb, as disclosed for example, in my Patent 2,035,426, granted March 24, 1936, on application, Ser. No. 634,019, filed September 20, 1932.

In accordance with this invention, generally speaking, it is proposed to provide for the ready adjustment of the time of operation of such enclosed thermal elements by varying the rate at which heat may be conducted or radiated from the heating element, either by changing the pressure of the gas in the enclosing bulb, or by changing the area exposed to the external air of a heat conducting member extending into the bulb into contact with the thermal element.

In certain applications of such thermal circuit controlling devices, it becomes necessary to operate a number of contacts to control circuits; and in accordance with this invention, it is pro posed to provide for the simultaneous operation of two or more thermal devices in such a way that their contacts are opened and closed synchronously.

The various characteristic features, advantages, and attributes of the invention will be in part apparent, and in part pointed out as the description progresses.

4 The accompanying drawings illustrate in a simplified and diagrammatic manner certain specific embodiments of the invention. Fig. 1 shows the structure of an enclosed thermal element having provision for adjusting the time of its operation by varying the pressure of the gas in the enclosed bulb. Fig. 2 is a fragmentary view illustrating the application of a'heat conducting part to an enclosed thermal element device for varying its time of operation; and Fig. 3

is another fragmentary view illustrating a modification of the heat conducting part. Fig. 4 illustrates an arrangement for operating a plurality of thermal circuit controlling devices so as to obtain substantially synchronous opening and closing of their contacts, for thepurpose of con-.

trolling lamps of a flashing signal "for highway crossings, or the like. Fig. 5 illustrates a modified form of the invention.

Referring to Fig. 1, the thermal device comprises a bi-metallic strip l of the usual type and "5 construction, such as brass and Invar strips fastened together. This member I is anchored at its lower end in the stem of a glass tube or bulb B, in the usual'way and in accordance with well-known practice. A similar bi-metallic strip 10 2 is Welded or otherwise rigidly fastened to the upper end of strip 1; and the two strips l and 2 are disposed in an opposing relation, so that they will be deformed in opposite directions by a change in the temperature of both, thereby main 15 taining the upper end of the two strips in substantially the same position with relation to the lower end, so as to compensate for gradual changes in ambient temperature. The lower strip l is heated by a coil or filament 3 oi suitable 20 resistance wire in the usual way, one end of this heating coil being soldered or welded to an anchor member 4 in the stem of the bulb B.

In the arrangement shown, two resilient contact members 5 and 6 are anchored at their lower 25 ends in the stem of the bulb B, and are connected together at the upper ends and to the bimetallic strip 2 by a tie-piece or driver member I of suitable insulating material, such as mica. Stationary contact members 8, 9, and Ill of 30 similar construction are anchored at their lower ends to engage the control members 5 and 6. These contact members may be made as a whole of suitable contact material, such as a nickel alloy; or contact pieces may be attached to these 35 members at the points of contact. One end of the heating coil 3 is connected to the contact member 5.

The arrangement of contacts illustrated is merely typical; and the contact members may be 40 arranged to open or close contacts in the heated or cooled condition of the thermal strip I.

The contact members and the anchor member 4 for'the heating coil are connected by wires to pins H in an insulating base C, attached to the 5 glass bulb or container B in accordance with regular practice.

In the embodiment of the invention illustrated in Fig. 1, a flexible metallic diaphragm l2 of bronze or other suitable material, preferably 5 corrugated, is attached to the upper end of the glass bulb B, the edge of this diaphragm forming a gas-tight seal with the glass. An adjusting nut l3 in a bracket or stirrup l4 suitably secured to the base C, is arranged to deform the dia- 55 phragm l2. After the parts have been assembled in the glass tube B and the tube is evacuated in accordance with the usual practice, it is preferably filled with inert gas such as argon or nitrogen, to a pressure conforming with the time characteristics desired.

When electric current is supplied to the heating coil 3, the temperature of the lower bimetallic strip is raised relative to that of the upper strip 2. Consequently, the upper end of the two strips is moved or displaced. This movement is assumed to be to the left to open contacts 5-3 and 5Hl, and to close contacts 6-43. The time taken to raise the temperature of the strip i sufiiciently to cause the necessary displacement to operate these contacts seems to depend on the rate at which heat may be conducted or dissipated, as well as the rate at which the heat is supplied. Experiments indicate that the rate at which the heat is dissipated from the thermal strip 1 is due to a large extent to conduction through the gas in the tube; and it has bee found that by varying the pressure of this gas, the rate of dissipation of the heat may be matcrially changed so as to increase or decrease within certain limits the time required to operate the contacts for the same heating current. Accordingly, this invention contemplates the provision of the diaphragm [2, or equivalent means, by which the pressure of gas within the tube can be readily varied after the device has been assembled, for the purpose of adjusting. the operating time of thermal operated circuit controllers, either to give the same time for a group of like devices in spite of manufacturing variations, or to adjust the same device for different operating times for different applications.

Fig. 2 illustrates another construction in which a heat conducting member I5 is welded or otherwise suitably fastened to the lower bi-metallio strip i, and is sealed in the glass bulb B with its outer end exposed to the atmosphere. It is contemplated that after assembly and test of the device, the area of the member l5 exposed to the external air may be changed by cutting it off to different lengths; and in this way the rate of dissipation of heat from the strip I may be varied to obtain the desired adjustment in operating time. This construction may be used with evacuated bulbs, as well as gas filled bulbs.

Fig. 3 illustrates a modification in the structure of the heat dissipating member I5 which is bent or shaped at its outer end for the attachment of a screw or the like of radiating disc or piece I5 the size and area of which can be selected to give the desired exposure and radiation to the atmosphere.

In some applications of thermal circuit controlling devices, as for example in the operation of the number of lamps for highway crossing signals, it becomes necessary to have a number of contacts operated concurrently and in substantial synchronism. These contacts may be necessary to control a number of devices that require separate control circuits, or in order to control current of a magnitude greater than can be readily handled by one pair of contacts, even though enclosed in an evacuated or gas filled tube. Accordingly, this invention further contemplates an arrangement for inter-connecting and controlling a plurality of thermal operated circuit controllers in such a way that the operation of their contacts will be in substantial synchronism, notwithstanding some variations in the time of heating and cooling of the different devices. Fig. 4 illustrates one arrangement for this purpose.

Referring to Fig. 4, it is assumed that the contacts 68 and B9 are to be used for controlling circuits for lamps that are to be lighted or flashed at regular intervals, as in a highway crossing signal; and it is further contemplated that the supply of current to light these lamps will be controlled in a suitable manner, as by the deenergization of a relay X, which by closing its back contact supplies current from one terminal of a suitable source marked to a bus 20 connected to the movable contact fingers 6 of the series of thermal devices, lamps L being connected to the stationary contacts 8 and 9 and to the other terminal of said source of current marked When the control relay X is deenergiaed, it also supplies current to a heating circuit including in series a plurality of adjustable resistance units R, RI, and R2, and also the contacts 5-I0 of one or more of the series of thermal devices. Each heating coil 3 of the thermal devices is connected across its corresponding resistance unit in the manner evident in the drawings.

By virtue of these electrical connections, the heating coil 3 of each thermal element is energized by the voltage drop across its corresponding resistance unit R; and by adjusting this resistance unit, the amount of current supplied to the heating coil may be varied for each thermal device independently of the others. Also, the heating circuit is interrupted by the opening of the contacts 5-H] of one or more of the thermal devices. As shown, the contacts 5ill oi the two of the three thermal devices are included in the heating circuit; but it should be understood that these contacts of only one of the thermal devices, or these contacts of all these devices may be employed to control the heating circuit.

It is contemplated that each of the series of thermal devices shown in Fig. 4 will be provided with means, such as illustrated in Figs. 1, 2, or 3, for adjusting or regulating the rate of dissipation of heat from the thermal element or bimetallic strip heated by the heating coil 3. By thus varying the rate of dissipation of heat from the thermal element, and by adjusting the resistance unit R. to vary the amount of current flowing in the heating coils 3, the time of opening and closing of the contacts 6-8 and 6-9 of each thermal device may be made substantially uniform notwithstanding manufacturing variations in the proportioning and positioning of the parts. In other words, such expedients for adjwstment make it possible to obtain substantially uniform heating and cooling times for the several thermal devices, which is desirable in the control of flashing lights for highway crossing signals, and the like. In this connection, it appears that the relative time required to heat and cool the bi-metallic strip l depends upon the rate of dissipation of heat from this thermal element, which makes the thermal element heat slowly and cool quickly, or vice versa. By varying this rate of dissipation of heat by the expedients already described, the heating and cooling time intervals may be made substantially the same for a given rate of heat supply; and by adjusting the resistance unit R, the appropriate rate of heat supply may be obtained for each thermal device of the series.

Desired simultaneous or synchronous at variously time related operation of the contacts controlling the lamps L is further assured by opening and closing the heating circuit for all of the thermal devices at the same time. It will be evident that this is necessarily the case Where the heating circuit includes the contacts 5-H] of only one of the thermal devices; and when the heating circuit includes these contacts of two or more of the devices, the circuit is opened by the contacts 5-H! of any one of the thermal devices, and is not closed until these contacts of all of the devices are closed.

The arrangement for inter-connecting and controlling a plurality of the devices as shown in Fig. 4 enables a series of contacts for controlling the circuits for a number of lamps or the like synchronously, and with substantially equal energized and deenergized periods. It is, of course, evident that the same expedients for obtaining substantially equal periods of energization and deenergization may likewise be employed to obtain unequal periods, if such is desired. For example, by variation of the pressures, or the resistances, or both, it can be so arranged for instance that the right hand thermal device closes its contacts 6-8 first, then the next to the left closes its, and finally the one at the extreme left closes its contacts. In this case, the contacts 5:!0 of the device at the extreme left would be the only contacts included in, and hence controlling, the series heating circuit.

The specific embodiments of the invention shown are merely illustrative; and various adaptations, modifications, and additions may be made to the specific constructions and arrangements of circuits shown and described, without departing from the invention.

What I claim is:

1. Apparatus for operating a plurality of contacts in a predetermined time relation, compris ing, a plurality of separate thermal-responsive contact operating devices each including a heating coil and a contact, and a series heating circuit for simultaneously supplying current to said heating coils and including separate means for varying the current supplied to each coil independently of that supplied to the others, said heating circuit being opened and closed by the operation of a contact of the one of said devices which operates last.

2. A plurality of thermal operated circuit controlling devices each including contacts, a bimetallic thermal element and a heating coil therefor for operating the contacts, an energizing circuit for said heating coils of said devices including variable resistances in series and controlled by contacts of one of said devices, each heating coil being energized by the drop in voltage across its associated resistance, whereby said heating coils may be simultaneously energized and deenergized by the closing and opening of said circuit and at the same time may be energized by different currents, and means for varying the rate of dissipation of heat from said thermal elements.

OSCAR S. FIELD. 

